Explosive Photographs

I’ve been reading some papers on early experiments in photography, and the things they tried astound me. Here’s an example:

By very carefully spreading a strong solution of the nitrate of silver over a
highly-calendered paper, and then exposing it to the perphosphuretted hydrogen slowly
evolved from the phosphuret of lime, a very even metallic surface was formed, from
the leaden colour of which it may be concluded some phosphorus had entered into
combination with the silver. This paper was soon attacked by the iodine, was little less sensitive than the silvered copper, but it was scarcely possible to remove the
iodine, so as to preserve the picture when complete, without portions of the surface
breaking away, so slight was the adhesion between the paper and the metal.

By allowing the paper to absorb the silver solution, and to become nearly, but
not quite dry before exposed to the gas, and the gas, which I usually form from phosphorus and solution of potassa, being liberated in large quantities, a black paper
possessing in a very eminent degree all that is desired, is the result.

Unfortunately, however, although I have used every precaution, I find it impossible
to prepare more than a dozen quarter-sheets without an explosion of the gas.
In placing and removing the paper, atmospheric air necessarily enters the vessel, besides
which, a quantity of oxygen sufficient to occasion spontaneous inflammation is
set free from the nitrate of silver and the water absorbed by the papers. On one occasion
I so placed and arranged some papers in a vessel as to do away with the possibility of any admission of atmospheric air ; the formation of the black phosphuret of silver was going on beautifully, when the large glass vessel burst with such violence that the largest piece H could find was but the sixteenth of an inch over.

I do not at present see any way of preparing those papers with safety, and, much
against any inclination, I have abandoned the use of this gas.

Robert Hunt, “On the Influence of Iodine in Rendering Several Argentine Compounds, Spread on Paper, Sensitive to Light, and on a New Method of Producing, with Greater Distinctness, the Photographic Image,” Philosophical Transactions of the Royal Society of London, Vol. 130 (1840), 325-334.

For the non-chemically inclined, Hunt was treating paper with nitric acid (which can transform the cellulose in the paper to nitrocellulose, or “guncotton”) and then introducing phosphorus and hydrogen gas to the mix. Needless to say, this is an explosive combination on many levels. It made great pictures, evidently—except for the little problem of the photographic paper having a tendency to explode. I’ve been looking for information on a photographic process created by Hunt called the energiotype mentioned by Root in 1864, and listed in an 1880 engineering encyclopedia. This early experiment seems rather energetic in itself.